Origin of Monster Ocean Waves

Physicists at the University of Lancaster, UK and Institute of Solid State Physics, Russia have for the first time discovered that wave energy can rapidly concentrate to create monster waves under some conditions, in contrast to previous work suggesting that it requires hundreds of miles of open sea for the waves to appear and disappear.

By using superfluid helium to model complex wave processes, researchers observed that monster waves in the laboratory developed by what is called an inverse wave energy cascade, whereby energy is forced to flow in a way that drives the rapid formation of abnormally large waves. Their results confirm theoretical predictions by the Russian mathematician Vladimir Zakharov of the University of Arizona and Landau Institute Russia.

For centuries monster waves (also known as rogue waves) have been blamed for occasional mysterious disappearances of ships and sailors. These giant, violent waves are believed to reach 100 feet or more in height, and are often described as a towering "wall of water." What makes them so dangerous is their tendency to emerge unexpectedly from relatively tranquil seas. It is the unpredictable nature of rogue waves that has prompted many to investigate their origins.

There is much interest in the origin of rogue waves, as they have huge adverse affects on maritime commerce and industry. If this new understanding can be exploited to explain how rogue waves arise on the ocean, it may be possible to predict them. -NR

Lumpy Life

B. HouchmandzadehPhysical Review Letters (forthcoming)

Even in a perfect world life would be imperfectly distributed, according to a new experiment performed at the Centre National de la Recherche Scientifique (CNRS) and Grenoble University in France.

Plants and animals tend to live near their relatives, rather than spreading out uniformly across the planet. Some of the clustering is due to variations in the environment, after all species are generally better adapted for certain types of conditions that for others. But physicist Bahram Houchmandzadeh discovered that even in a nearly perfect experimental environment, such as a petri dish with nutrients and living conditions that are uniform from place to place, amoeba clump together.

Houchmandzadeh attributes some of the clumping in his amoeba colony to the fact that newborn creatures start life close to their siblings. Although the microbes move about randomly, which smoothes out some of the lumpy distribution, it's not enough to erase the uneven distributions entirely. The experiment followed robust amoeba colonies as they grew, and did not address the effects of death or population fluctuations that occur in the real world. Houchmandzadeh, however, argues that such things would amplify the tendency of populations to cluster in groups.

The natural inclination toward clustering of plants and animals only partly explains population distributions in nature, but the new experiment shows that it is likely to be much more important than many researchers had previously suspected. -JR

50 Years of PRL

Martin Blume

Physical Review Letters turns 50 this year. Martin Blume is celebrating the green journal's birthday by summarizing the most intriguing papers to appear in PRL each year since 1958. To see past editions of Marty's Milestone PRL project, visit http://prl.aps.org/50years/milestones

This week, Marty is taking a look at milestone papers from 1981 and 1982 showing that no hidden variables can be responsible for weird quantum effects.

In these Letters, Aspect and collaborators experimentally tested the spacetime behavior of an entangled system. (While two of the Letters were published in 1982, they are included here as part of the 1981 Milestone selection.) According to quantum mechanics, strong correlations are to be expected between measurements performed on systems that have interacted, even though they are separated at the time of measurement. Consideration of these predictions had led A. Einstein, B. Podolsky, and N. Rosen [Phys. Rev. 47, 777 (1935); see also Physical Review Focus 16, story 10] to argue that quantum mechanics cannot be a complete description of reality. Nearly 30 years later, John S. Bell proved that certain inequalities must hold among polarization measurements performed on two separated particles which had previously interacted if, as Einstein and collaborators felt, quantum mechanics is underlain by local "hidden variables"; these inequalities can be violated in a purely quantum-mechanical system.

Aspect and collaborators tested Bell's inequalities as generalized by J.F. Clauser, M.A. Horne, A.Shimony, and R.A. Holt [Phys. Rev. Lett. 23, 880 (1969)], in a series of experiments which approached ever closer to the ideal experiment first envisioned by David Bohm, based on the concerns of Einstein, Podolsky, and Rosen. These experiments used pairs of correlated photons produced by laser excitations of an atomic radiative cascade. In the first Letter, the use of single-channel analyzers did not allow the direct measurement of all polarization states; two-channel analyzers were used in the second Letter to overcome this limitation. In the third Letter, variable polarizers were used to eliminate the possibility that unknown interactions among the measuring instruments could evade the inequalities. In these Letters, and in subsequent work by a number of groups, the results showed violations of the generalized Bell inequalities, in accordance with quantum mechanics and in disagreement with local hidden-variable theories. Thus, more than 45 years after the paper of Einstein, Podolsky, and Rosen, the gedankenexperiment suggested by their work was performed, with results that would have disappointed them. Further research on entanglement has led to the new field of quantum information.

Nadia Ramlagan and James Riordon contributed to this Tip Sheet.

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